Preliminary information is provided on physical and chemical characteristics of three aquatic systems in the pre-amazonian floodplain, Baixada Maranhense: Pindaré (Viana Lake) and the Pericumã and Turiaçu rivers. Emphasis is given to the nutrients analyzed spectrophotometrically from the bottom sediments of Viana Lake. The water bodies differ from each other with respect to conductivity, total suspended solids and nutrient contents in the water, with higher values (except for total nitrogen) in the dry season. The main factors responsible for such differences, besides the annual flood, are the presence of macrophytes on Pericumã, riparian vegetation on Turiaçu (both systems with lotic characteristics) and water buffalo at Viana Lake. Bottom sediments with low nutrient concentrations at Viana Lake may be due to the rapid mineralization of organic matter in this lentic environment.